I. Purpose and Scope of Art. 12 CO

1 Art. 12 CO is in principle a supplement to Art. 11 CO. Unless special provisions apply

, Art. 12 CO extends the formal requirements of contracts and any judicial acts as defined in Art. 11 CO to their amendments («Abänderungen», «modifications»). Contrary to its wording, Art. 12 CO not only applies when the law requires the simple written form for a judicial act, but also in the case of public notarization. However, Art. 12 CO does not apply if the parties have agreed on a specific form (see Art. 16 CO).

II. Amending/Modifying and Supplementing a Contract

2 Amending a contract or a specific provision therein, respectively, means either (i) modifying the contract or (ii) supplementing the contract by adding additional provisions without modifying its essential content.

• The modificationof a contract means that a contractual provision is either completely deleted or replaced by another (e.g. by changing a certain deadline, by allowing installments instead of lump sum payments or by modifying the pledge

  , etc.). Art. 12 CO also applies when a contract is transferred in its entirety to a third party.
  However, Art. 12 CO does not apply if the parties further describe or define already existing contractual obligations.
  This can be done in any form.

• By supplementing a contract pursuant to Art. 12 CO the parties add a provision to their existing (form-requiring) contract.

3 In practice, contracts can be amended/modified either by (i) destroying the old and issuing new contract documents/certificates, (ii) issuing separate addenda to the existing contract or (iii) correcting the relevant provision(s) by hand. However, it is not advisable to use the latter method due to the difficulty of future proofing.

III. «Supplementary collateral clauses»

4 As an exception to the above rule, Art. 12 CO refers to «ergänzende Nebenbestimmungen» or «stipulations complémentaires», which translate into English as «supplementary collateral clauses» of a contract.

5 Such «collateral clauses», which merely specify or supplement a contract or which only affect non-essential clauses of a contract, do not have to comply with any specific formal requirements, unless the provision(s) is/are in conflict with the original document. However, if a «collateral clause» contradicts the main contract, but does not itself have to meet any specific formal requirements (i.e. if it does not contain subjectively or objectively essential points of a contract

), it can, according to the Federal Supreme Court and most of legal doctrine, be concluded without any formal requirements.

IV. Art. 12 CO vs. 115 CO

6 Art. 115 CO has similarities with Art. 12 CO. According to Art. 115 CO, no particular form is required for the extinction of a claim by agreement even when the obligation itself could not be assumed without satisfying certain formal requirements required by law or elected by the parties. This means that, under certain conditions, a party may extinguish a debt without complying with any particular form.

7 In order to prevent contractual parties from circumventing Art. 12 CO, legal doctrine and case law have developed certain theories to distinguish between the two provisions. In the case of unilateral contracts (where only one party waives a claim), Art. 115 CO is supposed to override Art. 12 CO. However, Art. 115 CO does not apply in the case of a (synallagmatic) contract, unless all obligations are completely cancelled and the contract is revoked in its entirety.

Therefore, the conclusion of an (out-of-court) settlement does not fall within the scope of Art. 12 CO (as it does not qualify as a «modification», see above section II), and can thus be concluded without any formal requirements.

8 If an obligation is merely reduced or weakened for one party, as it is the case when only one party's obligation is cancelled or modified, Art. 12 CO remains applicable (as this is most likely to have a negative effect on the other party's obligation(s)).

9 In practice, it should be noted that, especially in the case of public notarization, the revoked act (e.g. a real estate transaction) might still appear in the land register (on which third parties may rely on in good faith).

V. Legal Effects if the parties fail to comply with Art. 12 CO

10 If the contractual parties amend their main contract without following the formal requirements, the amendment is considered invalid. The «old» contract remains in force.

Bibliography

Brütsch Susanne, Commentary to Art. 11 CO, in: Christoph Hurni/Mirjam Eggen (eds.), Onlinekommentar zum Obligationenrecht, https://onlinekommentar.ch/en/kommentare/or11, visited on 30.5.2023, (cit. OK-Brütsch).

Gauch Peter/Stöckli Hubert, Präjudizienbuch OR, Die Rechtsprechung des Bundesgerichts (1875–2020), 10. Edition, Zurich 2021.

Jäggi Peter, Commentary to Art. 12 CO, in: Schönenberger Wilhelm/Jäggi Peter (eds.), Zürcher Kommentar, Kommentar zum Schweizerischen Zivilgesetzbuch, Obligationenrecht, Kommentar zu den Art. 1–17 OR, 3. Edition, Zurich 1973 (cit. ZK-Jäggi).

Müller Christoph, Commentary to Art. 12 CO, in: Aebi-Müller Regina/Müller Christoph (eds.), Berner Kommentar, Obligationenrecht, Allgemeine Bestimmungen, Art. 1–18 OR mit Einleitung in das Schweizerische Obligationenrecht, Bern 2018 (cit. BK-Müller).

Schmidlin Bruno, Commentary to Art. 12 CO, in: Kramer Ernst/Scmidlin Bruno (eds.), Berner Kommentar, Obligationenrecht, Allgemeine Einleitung in das schweizerische Obligationenrecht und Kommentar zu Art. 1–18 OR, Bern 1986 (cit. BK-Schmidlin).

Schwenzer Ingeborg, Kommentierung zu Art. 12 OR, in: Widmer Lüchinger Corinne/Oser David (eds.), Basler Kommentar, Obligationenrecht I, 7. Edition, Basel 2019 (cit. BSK-Schwenzer).

Xoudis Julia, Commentary to Art. 12 CO, in: Thevenoz Luc/Werro Franz (eds.), Commentaire romand, Code des obligations I, 3. Edition, 2021 (cit. CR-Xoudis).